1. Field of the Invention
The present invention is in the field of manufacturing magnetic recording disks from a laminate of magnetic sheets on a base and stretching the sheets prior to completing the bonding to the base.
2. Description of the Prior Art
The prior art has provided examples of tension type magnetic disks wherein magnetic sheets are joined under tension to upper and lower surfaces of a relatively rigid base in such a manner that a narrow gap is held between the magnetic recording region of each sheet and the base. Such magnetic disks and a method of producing the same are disclosed, for example, in European Patent Application No. 186427. The method described in this application, however, presents a variety of problems. For example, it is not adapted for continuous manufacture since the magnetic sheets on the two surfaces must be tensioned by temporary holders and only a small tension adjustment range is possible for the two magnetic sheets. Furthermore, an annealing step is necessary to release the stress caused in the magnetic sheets due to the tensioning operation, and the annealing step must be performed independently of the bonding step. Therefore, the disclosed process provides operational difficulties and problems with respect to product quality.
Other types of stretched surface recording disks and methods for their manufacture will be found, in general, in the following U.S. Pat. Nos.:
4,365,257 PA0 4,464,693 PA0 4,543,619 PA0 4,573,096 PA0 4,573,097 PA0 4,581,667 PA0 4,623,570 PA0 4,625,384 PA0 4,631,609 PA0 4,670,072